Just one day after Inc. covered the formal launch of Mosaic, a clean energy crowdfunding platform based in Oakland that connects investors with solar energy projects, the start-up has made good on its promise: In less than 24 hours, it hasalready funded four sustainable energy campaigns in California.

On the company's blog, Billy Parish, Mosaic's president, wrote, "WOW. Thank you all so much...We are blown away, over 400 investors have put in more than $300,000 to fully fund our first publicly availble solar projects projects in less than 24 hours!"

The clean-energy projects, which will install solar panels on affordable-housing projects, are expected to give investors a yield of between 4.5% and 6.38% over a 20-year contract.

"We are thrilled at how the public showed up yesterday," said Mosaic's CEO, Dan Rosen. in a statement. "It's indicative of a pent-up demand that we are working to meet. People want strong returns and want to know what their money is invested in. Our marketplace allows people to sidestep Wall Street by investing in Main Street."

Want to invest in a clean-energy future? Forget the rhetoric. Now you can--literally.

Starting at noon ET on Monday, Mosaic becomes the first crowdfunding platform that will connect investors with clean-energy projects that need financing. For as little as $25, non-accredited investors (yep, just regular people!) in New York and California--as well as accredited investors around the country--can log on to Mosaic, review solar projects that need cash, and make direct investments in projects' developers.

The projects generate revenue by selling the electricity they produce, which then allows the investors to get paid back with interest. According to the company's co-founder, Billy Parish, the yield offered by the solar investments ranges from 4.5% to 6.38% annually, which is roughly on par with historical returns of the S&P 500.

For example, among a private group of investors in October, Mosaic raised $40,000 from 51 investors for a five-year, 6.38% loan to finance a solar project on the roof of a job-training center in Oakland.

"I looked at what the biggest constraints to the growth of clean energy were, and the biggest one was financing," says Parish. "There isn't enough money going into financing these projects. There are a couple of banks that are the primary sources of capital for these projects, and because there are so few players, the cost of capital is too high. I thought, We can bring down the cost of capital, bring a new, potentially major source of capital into the space, and build a constituency to get the policies we need to support the growth of the industry."

So far, the model appears to be working. Since the company privately launched in early 2011, it has deployed $1.1 million from more than 400 investors to fund a total of 11 projects.

Despite its apparent success, the process hasn't been simple. Parish says the company has worked tirelessly with the Securities and Exchange Commission, as well as state governments, to create a secure platform where investors are apprised of all the risk affiliated with making solar investments. Though the company has yet to achieve an official approval from the SEC, through Mosaic's working with state officials, both New York and California have allowed residents to begin making investments directly on the site.

"Every project comes with a prospectus that comes with the risk of the project," Parish says. "We look at multiple factors: equipment, the contracts associated, the developers, the installers. If we like the project, then we'll negotiate a loan."

Mosaic's business model is similar to that of a bank: It charges an origination fee up front to the developer and takes a 1% "skim" on top of the loan. (For example, if Mosaic makes a loan offer to a developer at 7%, it'll offer that as investment on the platform at 6%, keeping the 1% difference.)

"Happily, all of the projects so far have made on-time payments to our investors," Parish says. "No defaults, no problem so far."

Investors have high hopes for the start-up. The 14-person company has raised a total of $3.4 million in seed and Series A financing, as well as received a $2 million grant from the Department of Energy's SunShot Incubator Program, which funds up to $12 million in grant money to small businesses and entrepreneurs working on both hardware and software technology that makes solar more accessible for Americans.

"The market we're going after is the clean-energy market," Parish says. "The energy industry is the largest industry in the world. We are seeing a shift away from fossil fuels, and we're building a platform for people to participate in and benefit from the clean-energy revolution. The opportunity is enormous. We're aiming to be the leading investment platform for the clean-energy economy."